<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
    <style>
        /* 1.元素选择器/标签选择器 */
        h1 {
            color: red;
        }
        /* 2.class选择器/类选择器 */
        .c2 {
            color: blue;
        }
        .c3 {
            color: green;
        }
        /* 3.ID选择器 */
        #d1 {
            color: purple;
        }
    </style>
</head>
<body>
    <h3 id="d1">标题3</h3>
    <h3>标题3</h3>
    <h4>标题4</h4>
    <h1>标题1</h1>
    <h1>标题1</h1>
    <h2 class="c2">标题2</h2>
    <h2 class="c3">标题2</h2>
    <p class="c2">段落1</p>
    <p>段落2</p>
    <p>Lorem ipsum <span class="c2">dolor</span> sit amet, consectetur adipisicing elit. Atque deserunt doloribus, ex explicabo hic id iure officia perferendis quaerat, saepe sed voluptatibus! Amet eos eum nesciunt quas qui repellendus voluptas.</p>
</body>
</html>